The format of a US telephone number (TN) is NPA-NXX-XXXX. The first three digits is called the NPA (Numbering Plan Area) or area code. The first six digits of a TN is called the central office (CO) code. The full ten digits is called the line number, which is ultimately assigned to users. For example, for the telephone number (571) 434-5000, 571 is an area code assigned in Virginia, 571-434 is CO code assigned to Verizon Virginia, Inc. associated with the Herndon geographic area (e.g., rate center) and served from the switch HRDNVASTDS0, and 5000 is the line number assigned to the Neustar PBX. In some instances, the telephone number may be a non-geographic telephone number with no specifically associated geographic area. In such a case, the geographic area associated with the non-geographic telephone number would be, in effect, the entire country. When a user signs up for service, the service provider assigns a number from a pool of available numbers. Generally, these numbers are assigned at random. The available numbers are drawn from the blocks of numbers assigned to the service provider and consist of numbers not currently in use or which have not been used within a specific time period (e.g., preceding 90 days). In some geographic areas, all ten thousand telephone numbers in a CO code (NPA-NXX-0000 to 9999) are assigned to a service provider as inventory. In most geographic areas, one thousand telephone numbers identified by the first seven digits (NPA-NXX-X) are assigned to service providers as inventory. A service provider is required to acquire telephone numbers in such big blocks (one thousand or ten thousand). That is, even if the service provider needs one (or a handful) telephone number, it has to acquire a large block of telephone numbers. The existing system suffers from the disadvantage of being onerous to maintain because a service provider may be required to maintain a large inventory of numbers for a long period of time. As a result, extensive infrastructure may be required in terms of systems and personnel for numbering acquisition and management. The existing system also suffers from wastage because telephone numbers which are not assigned to a user remain unused. Moreover, the existing system does not allow a user to request a specific phone number (e.g., a novelty phone number) from the service provider.